Recent work has concentrated on the   development and use of an automated running wheel that can be used as   either an operant chamber or in discrete trials paradigms. The effect of   effortful responding on persistence is the current focus of this work.

Haddad, N.F., Szalda-Petree, A.D., Karkowski, A., Foss, R., Berger,   L., (1994). Wheel-running in discrete trial and operant paradigms under   various effort requirements. Physiology & Behavior, 56, 487-493.

Szalda-Petree, A.D., Karkowski, A., Brooks, L., & Haddad, N. F.   (1994). Monitoring running-wheel movement using a serial mouse and an   IBM-compatible system. Behavior Research Methods, Instruments &   Computers, 26 (1), 54-56.

Karkowski, A., Haddad, N. F., & Szalda-Petree, A. D. (1996). Rat   strategies and the interactive schedule: A multidimensional examination   of behavior. The Journal of General Psychology 123, 63-73.

Kirshenbaum, A., Szalda-Petree, A. D., & Haddad, N. F. (2000). Risk   sensitive foraging in rats: the effects of response-effort and   reward-amount manipulations on choice behavior. Behavioral Processes,   50, 9-17.

Kirshenbaum, A.P., Szalda-Petree, A.D., & Haddad, N.F. (2003).   Increased effort requirements and risk sensitivity: A comparison of   delay and magnitude manipulations. Behavioural Processes, 61, 109-121.

Animal Learning and Behavior, Research   Methods